Proximity-based applications and services represent a fast growing social and technological trend that may have a major impact on evolution of cellular wireless/mobile broadband technologies. These services are based on the awareness of two devices or two users being close to each other and may include such applications as public safety operations, social networking, mobile commerce, advertisement, gaming, etc. Device to device (D2D) discovery is the first step to enable D2D service. There are many unresolved issues with respect to device discovery for D2D communication particularly for inter-cell Proximity Service (ProSe) D2D discovery.